Any moons with moons?

PJay_A · Oct 30, 2008

Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it?

crazyeddie · Oct 30, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it? Posted by PJay_A</DIV>I don't believe there is any natural satellite of a satellite of a planet, although there's nothing physically impossible about the situation.  It's just that should a planet's moon acquire a moon of it's own, the tidal forces between it and it's new satellite would cause it's orbit to decay over time, until it eventually would crash into the surface of the primary moon, just as all the Lunar Orbiter satellites have done in the decades since they were launched in the Apollo era.  So in other words, a moon may have a moon of it's own, but it can't hold on to it for very long. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Oct 30, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it? Posted by PJay_A</DIV> Regarding the ISS, No not even close. Also it is too close to earth, so any object at that height will orbit earth. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

3488 · Oct 30, 2008

I think crazyeddie is correct.The lunar orbiters are an excellent demonstration of this concept. Our moon is large, got quite a respectable gravitational field of its own & quite far from Earth, so does have a reasonably sized Hill Sphere.Lunar Orbiters, both Manned & Unmanned are suseptable to lunar MASCONs (MASs CONcenentrations), regions under the Marial Lava plains where the gravity was slightly stronger than other areas, causing lunarcentric orbits to become unstable. Certainly other planetary moons have the potential of orbiting bodies around them. All four of the Jupiter Galilean Moons (Io, Europa, Ganymede & Callisto), Saturn's largest moons certainly (Tethys, Dione, Rhea, Titan & Iapetus, possibly Enceladus & Mimas, though they may be too small with being so close to Saturn), with Uranus, certainly Oberon, Titania, Umbriel & Ariel, maybe Miranda (though could be too small being so close to Uranus). Neptune's Triton should be possible. You may find this interesting, possible rings around Saturn's moon Rhea.  Replying to: <DIV CLASS='Discussion_PostQuote'>Regarding the ISS, No not even close. Also it is too close to earth, so any object at that height will orbit earth. Posted by MeteorWayne</DIV>The ISS, I agree is a no hoper. Very little mass & so close to Earth.Andrew Brown.  <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

vogon13 · Oct 31, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it? Posted by PJay_A</DIV> Delving into further solar system arcana, we might look at Cruithne, which, IIRC, alternates every century or two from an orbit about the sun resonant to Venus to one resonant with the earth/moon system. We also have Hyperion in a 4:3 resonance with Titan, and several other pairs of Saturnian satellites in 'near' resonances with each other. For those in the Iapetan equatorial ridge being an orbitally decayed ring system camp, note that ones' mass would far exceed the current oddiments orbiting Rhea.  Sadly, we be a few billion years late too see the darn thing running . . .        <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

JonClarke · Nov 1, 2008

There is always the ring round Rhea http://en.wikipedia.org/wiki/Rings_of_Rhea <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

PJay_A · Nov 2, 2008

Okay, what if a large satellite or space station was put into one of the "L" parking orbits between Earth and the Moon. In theory, could that satellite have smaller satellites orbiting it. Next question: What benefits could we possibly invent by creating orbiting sattelite pairs. I can't think of any, but I'm sure there's a use for such a technology to employ if the creatives out there could come up with one....

JonClarke · Nov 2, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Okay, what if a large satellite or space station was put into one of the "L" parking orbits between Earth and the Moon. In theory, could that satellite have smaller satellites orbiting it. Next question: What benefits could we possibly invent by creating orbiting sattelite pairs. I can't think of any, but I'm sure there's a use for such a technology to employ if the creatives out there could come up with one.... Posted by PJay_A</DIV>We already have satellites at some of these points for the Earth-Moon-Sun systemAdvanced Composition Explorer (ACE)L1Genesis L1International Sun/Earth Explorer 3 (ISEE-3) L1Solar and Heliospheric Observatory (SOHO) L1Wilkinson Microwave Anisotropy Probe (WMAP)L2Soon there will be:Herschel Space Observatory L2James Webb Space Telescope L2Planck satellite L2.   <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

h2ouniverse · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Posted by PJay_A</DIV> Yes!... in some way Rhea (one of the large Saturnian moons) has given hints recently that it should have faint rings, hence small particles orbiting it.http://www.nasa.gov/mission_pages/cassini/media/rhea20080306.html best regards.

DrRocket · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it? Posted by PJay_A</DIV>You would have to have the satellite of the moon in very close orbit in order that the gravitational field of the planet be negligible.  That is, in principle, possible as for example the observation that the Earth's moon orbits the Earth, and it only marginally affected by the Sun.  But given that moons tend to be fairly close to their respective planets, it would be difficult to have a satellite that clearly orbits the moon, with little effect from the planet.Once you have two gravitational fields affecting a satellite the problem becomes rather complex.  You, in fact, are faced with the three body problem and orbital solutions in that case are not known in closed form and require computer simulations.  They tend to not be stable orbits.  Instability rather precludes long-lived moons of moons.Sure there is enough gravity for an object to orbit the ISS.  VERY SLOWLY and VERY CLOSE.  Not a practical orbit at all. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>You would have to have the satellite of the moon in very close orbit in order that the gravitational field of the planet be negligible.  That is, in principle, possible as for example the observation that the Earth's moon orbits the Earth, and it only marginally affected by the Sun.  But given that moons tend to be fairly close to their respective planets, it would be difficult to have a satellite that clearly orbits the moon, with little effect from the planet.Once you have two gravitational fields affecting a satellite the problem becomes rather complex.  You, in fact, are faced with the three body problem and orbital solutions in that case are not known in closed form and require computer simulations.  They tend to not be stable orbits.  Instability rather precludes long-lived moons of moons.Sure there is enough gravity for an object to orbit the ISS.  VERY SLOWLY and VERY CLOSE.  Not a practical orbit at all. Posted by DrRocket</DIV> After all, there are satellites orbiting our Moon (three in fact at the moment IIRC) but they required very precise velocity and direction to but them there, and the orbits are not stable for very long (history of the solar system wise that is). <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

silylene · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>After all, there are satellites orbiting our Moon (three in fact at the moment IIRC) but they required very precise velocity and direction to but them there, and the orbits are not stable for very long (history of the solar system wise that is). Posted by MeteorWayne</DIV> I would think that either of the members of the KBO pair 2001 QW322 would perhaps be more likely to have a moonlet than just about anything else I can think of.  If this KBO pair were formed by a YORP spinup, as I suggested, or by collision, then there is a higher than average chance for a moonlet.  The KBO pair are so distant enough from one another that a moonlet orbit around one of them should be quite stable, even if it weren't all that close.Then in this case, you would have a moonlet of a binary plutoid ! <div class="Discussion_UserSignature"> petet = silylenePlease, please give me my handle back ! </div>

l3p3r · Nov 14, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Are there any known planets, such as Jupiter or Saturn, with moons that have its own natural satellites orbiting it (i.e. moons that have moons)?Another question, is there enough gravity onboard the ISS to allow anything to orbit it? Posted by PJay_A</DIV>It's not completely related... and I guess everyone has seen it already... but the Ida/Dactyl system is pretty neat! http://apod.nasa.gov/apod/ap990807.html <div class="Discussion_UserSignature"> </div>

vogon13 · Nov 14, 2008

I think we can expect binariation amongst the outer captured satellites of, for instance, Jupiter, to be similar in percentage to the presumed parent population of Jupiter Trojan  asteroids. I don't think we have any data on binary Jupiter Trojans yet, but it seems like at some point we will.  Light curve data on them or the Jupiterian outies would make a nice topic for a Phd thesis.     <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

franontanaya · Nov 15, 2008

Tricky answer: Nix and Hydra orbit Charon... partially. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-tongue-out.gif" border="0" alt="Tongue out" title="Tongue out" /> <div class="Discussion_UserSignature"> </div>

vogon13 · Nov 15, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Tricky answer: Nix and Hydra orbit Charon... partially. Posted by franontanaya</DIV> As the earth's moon orbits the earth moon barycenter, so to Nix andHydra, yada, yada, yada. What is significant about your post is, in the earth/moon case, the barycenter is always 1000 miles beneath earth's surface. Pluto/Charon's, on the other hand, is out in space where we can diddle with it. Bwa, ha, ha, ha !!    <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Mar 18, 2009

Regarding the Rhea materials;

I wonder if it would advance our thinking about this odd structure to contemplate it being rather more analogous to the asteroid belt than to Saturn's rings.

The density of the materials seems to be quite low, and the particle to particle interaction rate is apparently ~negligible.

I also note, there seems to be a suggestion the 3 main structures are near periodicities with the Rhea orbital period about Saturn. This may be somewhat suggestive of a resonant process possibly constaining the dissipation of the materials.

silylene · Mar 18, 2009

Speaking of odd fanciful structures:

1. Imagine a hollow planet, filled with a vaccuum. In this case I believe one could have a moon orbiting the center of mass, within the planet. This example would certainly stretch the definition of a 'moon.'

2. Imagine a hollow planet, with vacuum inside and out, which has two large openings or 'pores' between the inner and outer surface. In this case I believe one could have a moon orbiting the center of mass, in an elliptical orbit, going both outside and inside the hollow planet. Of course the planets rotation rate would need to be in perfect sync with the moon's elliptical orbit, to keep the pores aligned in order to prevent a collision with a surface.

I wonder if these cases have been modeled before?

If only i were a god, I would've had so much fun building my universe.

vogon13 · Mar 18, 2009

.

On the old board I had suggested a pipe around earth's equator at sea level with vacuum in it would be suitable for orbiting an object.

Also, IIRC, the proposed 5000 MPH undersea rail tunnel across the Atlantic would subject it's riders to (doing the math in my head) about .8 to.85G for the (brief) duration of their trip at speed. (assuming a great circle rout for the tunnel)

Your idea of an appreciable object orbiting inside a sphere is intriguing.

There might be some stable orbits circling the opening(s) too. Think about it.

silylene · Mar 18, 2009

vogon13":2k16xiza said:
.

On the old board I had suggested a pipe around earth's equator at sea level with vacuum in it would be suitable for orbiting an object.

Also, IIRC, the proposed 5000 MPH undersea rail tunnel across the Atlantic would subject it's riders to (doing the math in my head) about .8 to.85G for the (brief) duration of their trip at speed. (assuming a great circle rout for the tunnel)

Your idea of an appreciable object orbiting inside a sphere is intriguing.

There might be some stable orbits circling the opening(s) too. Think about it.

Your tunnel idea is fundamentally similar to my 'hollow earth' concept above.

On the "stable orbits circling the opening(s) too", are you perhaps suggesting a sort of Lagrangian-type L1 or L2 orbit within the shell ? I don't think that would work, but maybe I am not understanding your question. However, if you think about it, the Lagrangian points for a moon within a planet are rather intriguing. This would make a good paper, if I had the math skills.

Any moons with moons?

PJay_A

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